1. Field of the Invention
Embodiments disclosed herein relate generally to improved tool joints or other wear surfaces used in wellbore operations. In particular, embodiments disclosed herein relate generally to methods of applying wear resistant materials to and otherwise improving the properties of tool joints or other wear surfaces.
2. Background Art
Drilling wells for hydrocarbon recovery involves the use of drill pipes, to which at one end, a drill bit is connected for drilling through the formation. Rotational movement of the pipe ensures progression of the drilling. Typical pipes may come in sections of about 30 feet in length, and thus, these sections are connected to one another by a tool joint. Tool joints are the connecting members between sections of drill pipe—one member (the box) has an internal thread and the mating member (the pin) has an external thread, by which means they are assembled into a continuous unit with the drill pipe to form a drill string. Often, these tool joints have a diameter significantly larger than the body of the pipes, thus requiring protection against wear, particularly when drilling through highly abrasive, highly siliceous earth formations. In particular, as drilling proceeds, the tool joints rub against the drilled hole and/or drilled hole lining (i.e., casing). The strength of the connection is engineered around the wall thickness and heat-treated properties of the box above the thread. During drilling, the wall thickness above the thread thins as it rubs against the wall or casing. Thus, the life of the pipe is predicated upon the remaining strength of the tool joint.
Because increasing the life of the tool joint is desirable, there have been numerous attempts to provide weld a protective hardfacing alloy or cladding to the tool joint (or other wear prone surfaces such as a stabilizer or drill collar) to form a hardband. A variety of methods have been used to apply such wear-reducing materials to joints, including: GMAW (gas metal arc welding), GTAW (gas tungsten arc welding), PTA (plasma transferred arc), and FCAW (flux cored arc welding). These welding processes are characterized by establishing an arc between an electrode (either consumable or non-consumable) and a tool joint base material. Once this arc is established, intense heat forms a plasma. The gas that forms the plasma is furnished by means of an external gas or an ingredient from a tubular wire. The temperature of the plasma is in excess of 10,000 degrees Kelvin and is highest at the center of the weld, and decreases along the width of the weld.
Historically, and in practice, tool joints have been coated with tungsten carbide to resist the abrasion of the rock earth in the drill hole on the tool joint. However, tungsten carbide is expensive, it can act as a cutting tool to cut the well casing in which it runs, and the matrix is a soft steel which erodes away easily to allow the carbide particles to fall away.
Other prior art hardfacing materials used that are harder than siliceous earth materials are brittle and crack in a brittle manner after solidification and upon cooling due to the brittle nature of its structure and the inability of the structure to withstand solidification shrinkage stresses and typically emit sound energy upon cracking as well as causing considerable casing wear as previously stated. These hardfacing materials are alloys which belong to a well-known group of “high Cr-irons” and their high abrasive resistance is derived from the presence in the microstructure of the Cr-carbides of the eutectic and/or hypereutectic type.
Siliceous earth particles have a hardness of about 800 Brinell hardness number (BHN). In U.S. Pat. No. 5,244,559 the hardfacing material used is of the group of high Cr-irons that contains primary carbides which have a hardness of about 1700 Hv in a matrix of a hardness of at least 300 BHN to 600 Hv. These primary carbides at this high hardness are brittle, have little tensile strength and hence pull apart on cooling from molten state at a frequency that depends on the relative quantity of the primary carbides in the mix of metal and carbide. Thus, this type of hardfacing material, which is harder than siliceous earth materials, when applied by welding or with bulk welding, form shrinkage cracks across the weld bead. This material has been applied extensively and successfully during many years for the hardbanding of tool joints and hardfacing of other industrial products.
Although these materials have become and still are widely accepted by the trade, users expressed a desire for a hardbanding tool joint alloy combining casing-friendliness with the capability of being welded free of brittle cracks in order to minimize any concerns of mechanical failure risks. Indeed, in most industries (including the oil and gas industry's use of down hole drilling equipment) the metal components which make up the structure and equipment of a given plant must have integrity, which means being free of any kind of cracks, because such cracks might progress through the piece and destroy the part.
U.S. Pat. No. 6,375,865 describes an alloy having a martensitic-austenitic microstructure which is preheated before welding to the industrial product and cooled down after welding. Alloys of this structural type can be deposited crack-free (further aided by the pre- and post-treatments and are characterized by excellent metal to metal wear properties and low brittleness.
Wear by abrasion mechanisms always has been, and still remains a main concern in many segments of industry, including the drilling industry. However, there is some limitation on the types of materials that may be used due to limitations of their use with GMAW, GTAW, PTA, and FCAW, as well as limitations on the types of materials which do not harm the casing.
Accordingly, there is a continuing need for developments in methods of improving the properties of a tool joint or other wear surfaces by applying treatment techniques and/or material in order to increase the component's service life.